1. Field of the Invention
This invention relates to a light-transmitting type focusing screen for use in the optical finder of a single lens reflex still camera or a movie camera.
2. Description of the Prior Art
The mat surface of a focusing screen used in a camera has heretofore been shaped by pressing a heated plastic plate and plastic powder against a metal mold formed by applying a plating process to a metal surface formed with fine concavities and convexities by sandblast, and transferring the fine concavities and convexities of the metal mold onto the surface of the plastic plate. The surface of the focusing screen thus manufactured has the characteristic of causing the light transmitted through the focusing screen, i.e. the light travelling from the objective lens to the eye-piece portion, to be diffused within a relative wide angle range, and accordingly, the percentage of the light directed to the eye-piece portion is small and the finder picture plane is dark. The finder picture plane could be made bright by selecting a fine particle size of the sandblast and decreasing the height of the concavities and convexities during the manufacturing process of the focusing screen, but if this is done, the focus condition of the object image formed on the focusing screen will not change much between the in-focus state and the out-of-focus state and the resultant focusing screen will be low in focus detection accuracy.